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Ask Dr. Knowledge

How are artificial flavors made?

September 27, 2010

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How are artificial flavors made? I would have thought it would be harder to make artificial strawberry or grape flavor than just use extracts of real fruit.

There are really five basic tastes that the tongue can recognize: bitter, salty, sour, sweet, and umami. The last one is less familiar but corresponds to “savoriness’’ — a meatlike flavor. That taste can be produced by monosodium glutamate (MSG), which is why it is added to some food. For the other basic tastes, it is easy to find bitter, salty, sour, and sweet things that are cheap.

More complex tastes require that the sense of smell be included — something one tends to forget until a badly stuffed nose robs us of the pleasure of eating. You can make an extraordinary variety of smells by reacting acids containing a double-bonded oxygen with substances that have an oxygen and hydrogen dangling off them. As you might imagine from the vagueness of the description of the substances, there are zillions of combinations (called esters), and chemists making these could hardly help but notice the often fruity smells that were produced.

For example, if you react salicylic acid (from which aspirin is derived) with methyl alcohol, you get methyl salicylate, which is oil of wintergreen. Butyl acid and butyric acid react to make butyl butyrate, which smells like pineapple. Cinnamic acid and methyl alcohol make methyl cinnamate, which smells like strawberries.

Of course, natural products have complex mixtures of chemicals that make them smell and taste the way they do, so artificial flavors capture only part of the real thing. But economics makes the artificial smell and taste business huge nonetheless.

Not all artificial flavors are esters, but most other important artificial flavors are also small molecules. Why small? Being lighter, they have a better chance of evaporating into the air than larger ones, and what does not get airborne is not going to get to your nose.

Ask Dr. Knowledge is written by Northeastern University physicist John Swain. E-mail questions to drknowledge@globe.com or write to Dr. Knowledge, c/o The Boston Globe, PO Box 55819, Boston, MA 02205-5819.